1. Technical Field
The present invention relates to a droplet ejection head and a droplet ejection apparatus, more particularly, to a droplet ejection head and a droplet ejection apparatus provided with such a droplet ejection head.
2. Related Art
In a droplet ejection apparatus such as an ink jet printer, a droplet ejection head is provided for an ejecting droplet. It is known to public that such a droplet ejection head is provided with ink chambers (cavities) which store an ink therein and are communicated with nozzles for ejecting the ink as droplets, and piezoelectric elements which deform wall surfaces of the ink chambers.
In such a droplet ejection head, a part of the ink chambers (vibration plate) is deformed by expanding and contracting the piezoelectric elements for driving. By doing so, volumes of the ink chambers are changed, so that the droplets of the ink are ejected from the nozzles.
In the meantime, such a droplet ejection head is produced by bonding between a nozzle plate in which nozzles are formed and a substrate in which ink chambers are formed with a photosensitive adhesive agent or an elastic adhesive agent. JP-A-5-155017 is an example of the related art.
However, when an adhesive agent is supplied between a nozzle plate and a substrate, it is difficult to strictly control a supply amount of the adhesive agent. Therefore, it is impossible to uniform the supply amount of the adhesive agent, thereby forming an uneven distance between the nozzle plate and the substrate. This makes it possible to form ink chambers each having an ununiformity volume in a droplet ejection head.
Further, a distance between the nozzle plate of the droplet ejection head and a print medium such as a print sheet becomes uneven. Furthermore, there is a possibility that the adhesive agent is run out from a bonded part (between the nozzle plate and the substrate). These problems make it possible to reduce dimensional accuracy of the droplet ejection heard and quality of prints printed by the ink jet printer.
Additionally, the adhesive agent is exposed to an ink stored in the ink chambers for a long period of time. By exposing the adhesive agent to the ink for a long period of time, the adhesive agent changes properties thereof and is altered or deteriorated by organic components contained in the ink. For these reasons, there are possibilities that liquid-tight property of the ink chambers is lowered and components contained in the adhesive agent are dissolved in the ink.
On the other hand, it is known that respective parts constituting a droplet ejection head are bonded by a solid bonding method. The solid bonding method is a method in which these parts are directly bonded to each other without use of an adhesive layer constituted of an adhesive agent or the like. Examples of such a solid bonding method include a direct bonding method with silicon, a bonding method by using a cathode and the like.
However, the solid bonding method has the following problems: (A) constituent materials to be bonded are limited to specific kinds, (B) a heat treatment using a high temperature (e.g., about 700 to 800° C.) must be carried out in a bonding process, (C) an atmosphere in the bonding process is limited to a reduced atmosphere, (D) a part of regions between the parts of the droplet ejection head can not be partially bonded, and the like.